Light has been used for both illumination and communication for time immemorial. Surely, since shortly after humans harnessed the power of fire sharing light has been a way to express welcome and belonging. Of course, specific intentions can be expressed using light as well. In America, “one if by land, two if by sea,” is a famous example of the use of light to communicate information. Light sources such as bonfires, lanterns, and stoplights have long been used to communicate welcome, availability, and other information to those who can view the light provided by those light sources.